Tertullian

It is in expectation of this for himself that the apostle writes to the Philippians: "If by any means," says he, "I might attain to the resurrection of the dead. Not as though I had already attained, or were already perfect." And yet he had believed, and had known all mysteries, as an elect vessel and the great teacher of the Gentiles; but for all that he goes on to say: "I, however, follow on, if so be I may apprehend that for which I also am apprehended of Christ.